1. Field of the Invention
The present invention relates to a flat heat-exchange tube for use with a condenser, an evaporator, a heater core, and a radiator each of which is employed in an automotive air-conditioner for effecting a refrigerating operation, as well an to a method of manufacturing the flat heat-exchange tube. More specifically, the present invention relates to a heat-exchange tube in which a plurality of protuberances are formed so as to protrude inwardly.
The present application is based on Japanese Patent Applications No. Hei. 11-11113 and 11-22771, which are incorporated herein by reference.
2. Description of the Related Art
As shown in FIGS. 15 and 16, a known flat heat-exchange tube is formed from a plate 1 in which a plurality of beads 1A are formed so as to protrude to one side of the plate and a plate 2 in which a plurality of beads 2A are formed so as to protrude to one side of the plate. Specifically, the flat heat-exchange rube is formed by assembling the plates 1 and 2 such that the tops of the beads 1A and the tops of the beads 2A are connected together by means of brazing.
Another type of known flat heat-exchange tube is shown in FIG. 17. As shown in the drawing, the heat-exchange tube is formed by folding a single plate 4 into a flat tube, bonding opposite ends 4A, 4A of the plate 4, and inserting an inner fin 5 into the internal space of the flat tube.
FIG. 18 shows a still another type of a known flat heat-exchange tube. A flat heat-exchange tube A is described in Japanese Patent Publication No. Hei. 7-19774. The flat heat-exchange tube A comprises a flat main tube unit B through which a heat-exchange medium flows, and a plurality of cylindrical beads D which connect tube surfaces C, C, both mutually opposing within the main tube unit B, and cause turbulence in the flow of the heat-exchange medium. Reinforcement protuberances E are formed between a U-shaped bend portion B1 or the heat-exchange tube A and the main tube unit B, to thereby connect the tube surfaces C, C to the bend B1 in the longitudinal direction of the main tube unit B and to reinforce the bend B1.
In the flat tube A, a heat-exchange medium flowing through the main tube unit B is circulated while the plurality of beads D cause turbulence in the laminar flow of the heat-exchange medium, thereby improving a heat exchange efficiency.
Aforementioned known flat heat-exchange tubes have encountered the following problems.
In the flat heat-exchange tube shown in FIG. 15, when the plates 1 and 2 are brought into contact with each other, joints 3 which protrude from either side of the plates 1 and 2 in the widthwise direction thereof become deformed, as shown in FIG. 16, thus causing a brazing failure. Further, since the joints 3 protrude from the plates 1 and 2 in the widthwise direction thereof, the widthwise length of the heat-exchange tube becomes longer. The diameter of an unillustrated header pipe to which the flat heat-exchange tube is to be mounted becomes larger correspondingly.
In the flat heat-exchange tube shown in FIG. 17, the pressure applied to the joints of the plate 4 is made insufficient when the inner fin 5 is inserted into the internal space and becomes displaced, thus becoming more likely to cause a brazing failure.
In the flat heat-exchange tube A shown in FIG. 18, the plurality of beads D cause substantially two-dimensional turbulence in the laminar flow or the heat-exchange medium, and hence the thus-generated turbulence has a little affect of causing turbulence in a thermal boundary layer of hear-exchange medium developing in the vicinity of the tube surfaces C, C, thus limiting an improvement in heat exchange efficiency.